I. Field of the Invention
This invention relates generally to ball joint components intended for different applications involving a connection between two parts that require relative motion between them and that involve tensile and compressive loads, such as, for example, in suspension systems and steering systems of motor vehicles, and more particularly to a relatively low cost, long-lasting, ball joint capable of withstanding relatively high compressive and tensile loads.
II. Description of the Prior Art
Many different types of ball joints have been devised over the past 100 years for use on motor vehicles. The earlier designs comprised a metal housing having a spherical, concave socket for receiving a spherical metal ball of a ball stud therein. Because of the metal-on-metal construction, the mating parts experience rapid wear, even when the joint is regularly lubricated. Still other prior art designs have incorporated a compression spring for urging the socket with its spherical concave recess into intimate contact with the ball on the ball stud. See, for example, U.S. Pat. No. 6,020,212 to Littman. The presence of a spring in these designs necessarily results in internal play or clearance created during inward or compressive loading. Inherent with all springs, any load applied inward will deflect the spring and create a clearance condition and unwanted play.
Still other prior art ball joint constructions have incorporated a self-lubricating plastic insert for encasing the ball on the ball stud, but such arrangements have not been able to withstand high compressive loads such as those encountered in instances where the vehicle is made to jump and leave the ground. For example, persons driving all-terrain vehicles (ATVs) frequently traverse uneven ground at speeds that cause the vehicle to leave the ground and fly through the air for several feet before again slamming down onto solid ground. The heavy compressive forces encountered in such instances tend to extrude the plastic socket, thus resulting in premature failure. Further, when leaving the ground, a tensile force corresponding to the weight of the wheels and suspension components can cause many prior art ball joint components to fail. Other prior art ball joint designs, such as exemplified by the Yokoyama Patent 6,866,441 use components loaded from the bottom of the housing and are retained by the formation of a lip on the bottom surface of an end cap. When encountering high compressive forces such as can be developed when operating an ATV, the downward force of the ball against the end cap can spread the lip causing the ball joint to fail.
It is accordingly a principle object of the present invention to provide an improved ball joint construction for use in motion transfer applications including, but not limited to suspension and steering systems on automobiles, trucks, ATVs, snowmobiles and other on and off road vehicles.
Another object of the invention is to provide a ball joint construction that eliminates the need for the traditional spring component commonly used with the prior art.
Still another object of the invention is to provide a ball joint construction in which the components thereof are loaded through the top of the ball joint housing and then retained by forming a lip on the top of the housing making it capable of accommodating high compressive forces.
Yet another object of the invention is to provide a ball joint construction where the ball on the ball stud constitutes substantially one continuous spherical surface so that full surface contact and maximum support of the ball stud from the internal components is achieved.
Yet another object of the invention is to provide a ball joint construction incorporating a molded plastic cup incorporating a metal spider, each having a concave spherical recess for receiving the spherical ball on the ball stud, but which is not subject to extrusion deformation under relatively high compressive loads.